Raman谱研究不同缓冲层结构对Si_(1-x)Ge_x应力弛豫的影响

应用 Raman散射谱研究超高真空化学气相淀积 ( UHV/CVD)生长的不同结构缓冲层对恒定组分上表层 Si1- x Gex 层应力弛豫的影响 .Raman散射的峰位不仅与 Ge组分有关 ,而且与其中的应力状态有关 .在完全应变和完全弛豫的情况下 ,Si1- x Gex 层中的 Si- Si振动模式相对于衬底的偏移都与 Ge组分成线性关系 .根据实测的 Raman峰位 ,估算了应力弛豫 .结果表明 :对组分渐变缓冲层结构而言 ,超晶格缓冲层中界面间应力更大 ,把位错弯曲成一个封闭的环 ,既减少了表面位错密度 ,很大程度上又释放了应力     

Experimental validation of mechanical stress models by micro-Raman spectroscopy

It is shown that micro-Raman spectroscopy offers a unique tool for the validation of stress models for microelectronics devices. Starting from an analytical or numerical model that describes the variation of local stress in a device, the corresponding Raman shift is calculated and compared with the data. In this way feed-back is given to the model. This technique is demonstrated for stripes (Si₃N₄, COSi₂, W) on a Si substrate, but can be applied to any device where Raman data can be obtained.     

Strain Relaxation Related Photoluminescence Bands in Ge／Si Short Period Superlattices

Pure-Ge/Si short period superlattice (SPS) grown by gas source MBE(GSMBE) is studied by photoluminescence spectroscopy and Raman scattering spectroscopy.An abnormal band in photoluminescence is found in an intermediate range of Lsi between 1.9nm-2.9nm for samples with Lge fixed at 1.5ml.In contrast to a pure-Ge/Si quantum well,the energy of the band shows red-shift as Lsi increases .Raman scattering shows that Si-Si vibration related Raman shift reaches a minimum for samples with strongest PL intensity of the abnormal band .It is therefore concluded that the abnormal band is related with strain relaxation process.     

热壁外延生长GaAs／Si薄膜质量研究

本文研究了用热壁外延（HWE）技术在Si衬底上不同工艺下生长的GaAs薄膜的拉曼（Raman)和荧光（PL）光谱。研究表明：在室温下,GaAs晶膜的Raman光谱的265cm^-1横声子（TO）峰和289cm^-1纵声子（LO）峰的峰值之比随晶膜质量的变化而逐渐变大、半高宽（FWHM）变窄且峰值频移动变小,而LC光谱出现在871nm光谱的FWHM较窄,表明所测得的薄膜为单晶晶膜,对同一晶膜也可判断出均匀程度。因此可以通过拉曼光谱和PLC光谱相结合评定外延膜晶体质量。     

Effects of Copper Plasticity on the Induction of Stress in Silicon from Copper Through-Silicon Vias (TSVs) for 3D Integrated Circuits

Finite element modeling (FEM) has been undertaken to characterize the effect of copper (Cu) elasto-plastic behavior on the induction of stress in 3D crystalline silicon (Si) systems incorporating Cu through-silicon vias (TSVs). Using a linear isotropic hardening model, simulations of thermal annealing cycles in Cu TSVs indicate that, for sufficient anneal temperatures, plastic yield within the Cu leads to substantial residual stress in the neighboring Si following cool-down. Simulated Si stress profiles of annealed isolated TSVs agreed with experimental Raman microscopy measurements of post-anneal stress profiles in Si near isolated 5 × 25 μm cylindrical TSVs on a 300 mm Si wafer. Simulations were expanded to investigate the impact of Cu plasticity (yield stress and tangent modulus) on the residual stress profile in Si near isolated TSVs and linear TSV arrays. The results show that the magnitude and extent of the TSV-induced stress field in Si is a non-monotonic function of Cu yield stress. Moreover, the tensile or compressive nature of TSV-induced stress within and outside linear TSV arrays is also a strong function of the Cu yield stress. The simulated impact of Cu tangent modulus on TSV-induced stress in Si is less substantial. The implications of these results for TSV layout with respect to active device placement in a 3D system are discussed.     

6H-SiC同质外延层上Si1-yCy合金的生长

用化学气相淀积(CVD)的方法, 在6H-SiC衬底上同质外延生长SiC层, 继而外延生长了Si1-yCy合金薄膜, 用X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼散射等方法对所得的样品进行了表征测量, 着重研究了生长得到的Si1-yCy合金的晶体结构。SEM结果显示6H-SiC外延层上生长的Si1-yCy合金薄膜表面平整, 晶粒大小均匀; XRD衍射谱仅显示单一的特征衍射峰(2θ约为28.5°), 表明得到的合金薄膜晶体取向单一, 其晶体类型为4H型; 粗略估算, 合金薄膜中C含量约为3.7%。拉曼谱显示：随生长气源中的C/Si比的增加, Si1-yCy合金薄膜中替位式C含量逐渐增大, 当C/Si比达到一定值时, 合金薄膜中有间隙式C出现, 造成晶体缺陷, Si1-yCy合金薄膜晶体质量下降。     

GaN基LED与Si键合技术的研究

采用金属键合技术结合激光剥离技术将GaN基LED从蓝宝石衬底成功转移到Si衬底上。利用X射线光电子谱(XPS)研究不同阻挡层对Au向GaN扩散所起的阻挡作用,确定键合所需的金属过渡层。利用多层金属过渡层,在真空、温度400℃和加压300 N下实现GaN基LED和Si的键合,通过激光剥离技术将蓝宝石衬底从键合结构上剥离下来,形成GaN基LED/金属层/Si结构。用金相显微镜及原子力显微镜(AFM)观察结构的表面形貌,测得表面粗糙度(RMS)为12.1 nm。X射线衍射(XRD)和Raman测试结果表明,衬底转移后,GaN基LED的结构及其晶体质量没有发生明显变化,而且GaN与蓝宝石衬底间的压应力得到了释放,使得Si衬底上GaN基LED的电致发光(EL)波长发生红移现象。     

The formation of silicon nanocrystals in SiO<Subscript>2</Subscript> layers by the implantation of Si ions with intermediate heat treatments

The effect of heat treatments at 1100°C on an ion-beam synthesis of Si nanocrystals in SiO₂ layers is studied. The ion-implanted samples are subjected either to a single heat treatment after the total ion dose (10¹⁷ cm^?2 has been implanted, two heat treatments (a heat treatment after the ion implantation of each half of the total dose), or three heat treatments (a heat treatment after each third of the dose). The total duration of the heat treatments is maintained at 2 h. It is found that the intermediate heat treatments lead to a shift of the Raman spectrum of the nanocrystals to longer wavelengths and to a shift of the photoluminescence spectrum to shorter wavelengths. Study using electron microscopy shows that the size of the nanoprecipitates decreases, which is accompanied by the disappearance of the characteristic features of crystallinity; however, the features of photoluminescence remain characteristic of the nanocrystals. The experimental data obtained are accounted for by a preferential drain of Si atoms to newly formed clusters, which is consistent with the results of a corresponding numerical simulation. It is believed that small nanocrystals make the main contribution to photoluminescence, whereas the Raman scattering and electron microscopy are more sensitive to larger nanocrystals.     

激光法制备纳米氮化硅及其光谱特性研究

介绍了激光诱导化学气相沉积法制备纳米氮化硅的工艺原理,通过增加正交紫外光束激励NH3分解,提高气相中n(N)/n(Si)比,从而减少产物中游离硅的浓度,制备出粒径7～15 nm的无团聚、理想化学剂量(n(N)/n(Si)=1.314)的非晶纳米氮化硅粉体.采用透射电子显微镜观察粉体形貌,并指出表面效应和量子尺寸效应导致粉体红外吸收光谱和拉曼光谱的"蓝移"和"宽化"现象.采用双光束激励的光诱导化学气相沉积法是制备高纯度纳米氮化硅粉体的理想方法.     

Strain Reduction in Selectively Grown CdTe by MBE on Nanopatterned Silicon on Insulator (SOI) Substrates

Silicon-based substrates for the epitaxy of HgCdTe are an attractive low-cost choice for monolithic integration of infrared detectors with mature Si technology and high yield. However, progress in heteroepitaxy of CdTe/Si (for subsequent growth of HgCdTe) is limited by the high lattice and thermal mismatch, which creates strain at the heterointerface that results in a high density of dislocations. Previously we have reported on theoretical modeling of strain partitioning between CdTe and Si on nanopatterned silicon on insulator (SOI) substrates. In this paper, we present an experimental study of CdTe epitaxy on nanopatterned (SOI). SOI (100) substrates were patterned with interferometric lithography and reactive ion etching to form a two-dimensional array of silicon pillars with ～250 nm diameter and 1 μm pitch. MBE was used to grow CdTe selectively on the silicon nanopillars. Selective growth of CdTe was confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Coalescence of CdTe on the silicon nanoislands has been observed from the SEM characterization. Selective growth was achieved with a two-step growth process involving desorption of the nucleation layer followed by regrowth of CdTe at a rate of 0.2 Å s^?1. Strain measurements by Raman spectroscopy show a comparable Raman shift (2.7 ± 2 cm^?1 from the bulk value of 170 cm^?1) in CdTe grown on nanopatterned SOI and planar silicon (Raman shift of 4.4 ± 2 cm^?1), indicating similar strain on the nanopatterned substrates.     

Effect of the ion-energy loss rate on defect formation during implantation in silicon nanocrystals

The effect of irradiation with He⁺, F⁺, and P⁺ ions with various energies on photoluminescence and structure of Si nanocrystals is studied. It is established that, at low intensities of ion losses, quenching of photoluminescence is provided by individual atomic displacement. However, as this intensity is increased, quenching is accompanied by an increase in nuclear losses. It is believed that, in low-density displacement cascades, mobile defects predominantly drain to the surface, where they form the centers of nonradiative recombination. In contrast, mobile defects partially form stable structural defects within the nanocrystals in dense cascades. It is sufficient to accumulate ～0.06 dpa for amorphization of Si nanocrystals at 20°C; dependence of this effect on the intensity of the ion energy loss was not observed. It was also noted that there is a low probability of annihilation of vacancies and interstitials within Si nanocrystals; this effect is attributed to the presence of an energy barrier.     

Ge/Si量子点的控制生长

采用离子束溅射技术,在生长了Si缓冲层的硅晶片上制备了一系列Ge量子点样品.借助原子力显微镜(AFM)和Raman光谱等测试手段研究了Ge/Si量子点生长密度、尺寸及排列均匀性的演变规律.结果表明,改变Si缓冲层厚度及其生长方式,可以有效控制量子点的尺寸、均匀性和密度.随缓冲层厚度增大,量子点密度先增大后减小,停顿生长有利于提高缓冲层结晶性,从而提高量子点的密度,可以达到1.9×1010 cm-2.还研究了Si缓冲层在Ge量子点生长过程中的作用,并提出了量子点的生长模型.     

Ranlan测量Ge/Si多层膜中Ge晶粒尺寸的理论研究

研究了用磁控溅射方法制备的Ge     

Simultaneous operation of a Raman fiber amplifier and laser pumped by a dual-wavelength Nd/sup 3+/-doped fiber laser

This paper presents an experimental study on the dynamics of Raman fiber lasers that use highly GeO/sub 2/-doped fibers as an active medium and a dual-wavelength (1060 and 1090 nm) Nd/sup 3+/-doped fiber laser as a pump source. The 1090-nm pump wavelength is located within the SiO/sub 2/ Raman gain spectrum relating to the 1060-nm pump wavelength, and competition is observed between Raman amplification of the 1090-nm emission with the 1060-nm emission used as the pump source and Raman lasing, which is independent of the 1090-nm amplification and which is also uses the 1060-nm emission as the pump source. Several pump configurations have been demonstrated to generate specific Stokes emissions generated through Raman lasing or amplification. Changing the gain-to-loss ratio by introducing intracavity loss of Raman emissions or increasing the Raman fiber length within each configuration can force either Raman amplification or lasing to dominate. The maximum slope efficiency as a function of the launched pump power was /spl sim/55% with a total output power of 1.6 W produced. A red shift of both the pump and the Stokes wavelengths is experimentally observed when the launched diode pump power is scaled up.     

磁控溅射Ge/Si多层膜的发光特性研究

采用磁控溅射技术,在Si(100)衬底上制备了一系列不同周期、不同Ge层厚度的Ge/Si多层膜样品.用室温光致发光(PL)、Raman散射和AFM图谱对样品进行表征.结果表明:Ge/Si多层膜中的PL发光峰主要来自于Ge晶粒,并且Ge晶粒生长的均匀性对PL发光影响较大,生长均匀的Ge晶粒中量子限域效应明显,随着晶粒的减小,PL发光主峰发生蓝移;在Ge晶粒均匀性较差时,PL发光峰强度较弱,量子限域效应不明显.     

Raman characterisation of stress in recrystallisedsilicon-on-insulator

Raman scattering measurements were carried out to characterise Si films deposited on SiO₂-coated Si substrates and recrystallised by a graphite strip heater or Ar⁺ ion laser. The frequency downshifts of the Raman peaks demonstrate that the Si films are under tensile stress. The crystallinity of the recrystallised films is also discussed     

Thermal Metrology of Silicon Microstructures Using Raman Spectroscopy

Thermal metrology of an electrically active silicon heated atomic force microscope cantilever and doped polysilicon microbeams was performed using Raman spectroscopy. The temperature dependence of the Stokes Raman peak location and the Stokes to anti-Stokes intensity ratio calibrated the measurements, and it was possible to assess both temperature and thermal stress behavior with resolution near 1mum. The devices can exceed 400degC with the required power depending upon thermal boundary conditions. Comparing the Stokes shift method to the intensity ratio technique, non-negligible errors in devices with mechanically fixed boundary conditions compared to freely standing structures arise due to thermally induced stress. Experimental values were compared with a finite element model, and were within 9% of the thermal response and 5% of the electrical response across the entire range measured     

纳米硅量子点/氮化硅三明治结构的电致发光

采用等离子体化学气相沉积技术制备了两种不同非晶硅层厚度的氮化硅/氢化非晶硅/氮化硅三明治结构,研究了不同能量激光退火对薄膜晶化的影响。通过拉曼分析,发现在激光能量为320mJ时,样品开始晶化,随着能量的提高晶化程度增加,在340mJ时达到最大。根据拉曼晶化峰的偏移,计算得出硅量子点尺寸为2.8nm和4.7nm,表明三明治结构对形成的硅量子点的尺寸具有限制作用。设计并制备了基于该结构的电致发光器件,在偏压大于10V时,在室温下可观测到电致发光。发现不同激光能量下晶化后的样品的电致发光强度不同,发光峰位在680nm和720nm附近。分析表明电致发光来源可以归结为电子空穴对在硅量子点中的辐射复合发光。     

Combined influence of third-order dispersion,intra-pulse Raman scattering,and self-steepening effect on soliton temporal shifts in telecommunications

Here, we discuss the influence of higher-order nonlinear effects like third-order dispersion, intra-pulse Raman scattering, and self-steepening effects on 1-ps soliton pulse shift or displacement from its initial position. The temporal shifts of soliton due to these higher-order nonlinear effects were studied numerically by “Method of Moments” to realize the contribution of these HOE on shifts. Further, we note the influence of positive and negative TOD on the shift produced by the combined HOE. The soliton shift is then analyzed in 160-Gbps telecommunication system implemented with conventional single-mode fiber (C-SMF) for the length 10 and 20 km. The disturbances between the adjacent soliton pulses in noted with different 16-bit data sequences, and the deterioration of system is characterized in terms of quality factor. It could be seen for an unchirped soliton of pulsewidth \(T_{\mathrm{o}}\sim 1\hbox {ps}\), the shift is highly influenced due to intra-pulse Raman scattering, while the shifting due to third-order dispersion can be treated negligibly small. Moreover, negative TOD was expected to inhibit the soliton temporal shift such that it would reduce collision with adjacent pulses; it results in more resonant radiation resulting in pulse decaying. Although negative TOD helps in good reception of pulses for 10 km, it fails to perform in system with 20 km C-SMF, where the dispersive components break more and more while traveling along the length of fiber.     

Raman测量Ge／Si多层膜中Ge晶粒尺寸的理论研究

研究了用磁控溅射方法制备的Gex/Si1-x多层膜的Ge拉曼光谱，在分析了多层膜中Ge微晶的分布和采用微晶壳层 结构假设的条件下，考虑了微晶表面效应的影响，用声子限域模型计算了Ge纳米晶粒的拉曼谱线，拉曼拟合谱线为三条理论谱线的叠加。计算结果表明：在考虑了微晶的表面效应后，拟合结果与实验结果符合得很好。